1951 G80s, Burman CP Gearbox...SUCCESS.

[GrayKay]

Hi Everyone
Still having gearbox problems with my fully restored 51 Matchy G80s, Burman CP model.
Has anyone got specific knowledge of this box...

The engine hasent been started yet, I found this problen when I wheeled it along the floor for the first time off the work bench...

With THE ENGINE NOT RUNNING... works great on the stand, gets all the gears by hand changing, no noise when the wheel is rotated...but lower it to the ground and roll her forward, and graunching trying to find a gear... back up on the centrestand and wheel rotates sweetly... no issues.
What have I missed ????
Last thing to fix before I ride her.
Cheers Gray.
On the Gold Coast, Queensland, Australia.

Forgot to mention... the box was good before we started the restoration, rode well with no odd noises, I reckon we would have noticed these crunchy sounds before we started...

[Trefor]

Difficulties with gear change are usually something to do with the clutch especially its adjustment. I'd start there.

[Ralph]

+1 for the clutch, not freeing off properly, are the springs adjusted so the pressure plate lifts evenly.

[GrayKay]

No, The Engine hasent been started yet, this is gears crunching trying to find a gear by just pushing along the floor...

Waiting to start, but I live with a very steep driveway so ALL things have to work before I ride for the first time, or I wont be able to get back up the drive.

Thanks for your answers, I just didnt explain fully.

[SPRIDDLER]

Still having gearbox problems with my fully restored 51 Matchy G80s........

Presumably by 'fully restored' you've had the primary drive and clutch apart but have you been inside the gearbox?
If you haven't touched the 'box I too would suspect the clutch, but I see in your Profile that you've had a 350 AJS with a CP 'box for 50 years so presumably you know your way around setting up these transmissions.

[GrayKay]

Hi Spriddler..
Thanks, but no, the 52 Ajs has the B52 gearbox, never had any issues there.

Yes, the gearbox has been spread over my work bench 58 times now... just looking for that one thing I have missed.
I replaced the main shaft oil seal behind the sprocket, and the main shaft bearing at the kick start ratchet end...
I have been over all the photos I took when we stripped the box, but all seens good... except for the one thing I can't find !!!!

[SPRIDDLER]

Yes, the gearbox has been spread over my work bench 58 times now..

Hmm, hadn't realised that.
Can't really help much from here but there are a couple of articles with diagrams in Christians Archive under 'Transmission' which may have a clue.
Here's just one of them as an example............

http://archives.jampot.dk/technical/Tra ... b_1941.pdf

[GrayKay]

Cheers Spriddler, I have read that and the others there...
Keep thinking, its staring at me... just cant see it.

[g80csp11]

with engine running and primary cover off is the clutch centre stationary and quiet when clutch is disengage, if yes its not the clutch
clutch basket has a thick and thin washer, see illustration 17 on page 46
thick one first on assembly otherwise basket will potentially rub on inner chain case

http://archives.jampot.dk/book/Owners_m ... Manual.pdf

[SPRIDDLER]

Although I've had a couple of bikes with the CP 'box I've never had to delve inside them so I can only surmise.
However, upon further thought it occurs to me that I've read on the forum of several 'box issues after rebuild or parts replacement being due to incorrect end float of the shafts. This has generally been the result of using gaskets that were too thick or too thin, or using a liquid sealant instead of a gasket. You have replaced a seal and a bush and being down under and away from easy parts supply you may have made the gaskets yourself or used sealant instead.